Air-speed control and spin delay assembly for link trainers



I N VE N TOR l LSHEQMNA, /f/OABEPT vBY Eh l 5 `2 Sheets-Sheet l A TTORN E YJ s. A. HOLBER'T IFiled Feb. 29, 1944 AIR SPEED CONTROL ND SPIN DELAY ASSEMBLY FOR LINK TRAINERS Nov. 14, 1944.

Nov. 14, 1.944. 5 A HQLBERT I 2,362,486

" AIR SPEED CONTROL AND SPIN DELAY ASSEMBLY FOR LINK TRAINERS Filed Feb.r 29; 1944 l 2 sheets-sheet 2.y

Y i L A C M-ATTORNEYJ Patented Nev. 14, '1944 UNITED STATES PATENT oEFIcE AIR-SPEED-CONTROL AND SPIN DELAY Y' ASSEMBLY FOR L INK TRAINERS Sherman AA. Hulbert: Manchester, Iowa Application February 29,1944, serial Ne.524,436

(Granted umleitlie act oi.' March-3, 1883, a-s amended April 30, 1928; 370 O. G. 757) 6 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon. I

This invention relates to improvements in instrument flying trainers, especially the so-called Link trainers, manufactured by Link Aviation Devices, Inc. of Binghamton, New York, and employed by the Army Air Forces in the training of pilots. When a Link trainer is placed in opera-v tion and a student climbs into it, the stall lvalve is in the spin position, since application of vacuum to the stall valve bellows is necessary for normal operation; consequently, the trainer bey gins to spin immediately upon turning on the turbine which provides a source of vacuum for all the diiierent vacuum-operatedv parts of the .trainen Heretofore it has been necessary for the instructor, prior to turning on the turbine, to removel a side panelfrom the trainer fuselage and reach in and take hold of the inverted pendulum which is a part of the stall valve assembly, so that th student could climb int'o the trainer and be seated and assume full "control without being subjected to the spin. lOne object of the invention is to provide a mechanism which will automatically prevent the trainer from spinning when the turbine is rst turned on, while permitting all parts of the trainer to function n ormally at all other times. Present Link trainers are also decient in that the student may not practice instrument take-offs. All training in present Link trainers must start with thestudent in the trainer in normal ilight attitude and Astarting from a predetermined altitude. Another object is to provide a mechanism which will permit accurate instrument indication for an instru*- ment take-oil, so that this procedure may be taught to and practiced by the student. Further objects are to provide a device for the stated purpose whose costis reasonable, which requires little maintenance, and which may be installed pairment of their functions. y

Reference may be made to Link Patent No. 2,099,857, dated November 23 1937, for an understanding of the general nature of the Link trainer.

In the accompanying drawings showing the preferred form of the invention.

sition, and indicating in dotted lines the unlatched position, the pendulum parts being omitted;

Fig. 3 is a series of sections on lines 3cr-3a, 31a-3b and 3c-3c, Fig. 2, showing the positions of the three valve ports in positions A, B and C (Fig. l) ofthe inverted pendulum;

Fig. 4 is a wiring diagram; and

Fig. 5 is a fragmentary elevation of end of a Link trainer with the fuselage wall broken away to show the preferred location of the improvement. g

vReferring particularly to the drawings, and

` mst to Fig. 1, the throttle 1ever. II is pivoted lever is pushed forward, the simulated air speed of the trainer increases, and when `it is pulled backward, the indicated air speed is lowered. Pivotally secured to lever I3 is a link I8 whose other end is pivotally connected to walking beam Il between the upper and lower ends of the latter. The lower end of walking beam -Il has a springcompensated rod I8 connecting it mechanically with the climb-dive valve assembly, not shown. A

` without alteration of the trainer parts or im- Fig. 1 is a schematic perspective view of part bell crank lever I9 is pivotally connected as'at 20 to the upper end of the walking beam, and is rigidly secured at its lower end to one end of a torque rod 2|, which is a horizontal rod extending laterally of the trainer and adapted to rockon its axis in journals supported by a pedestal 22 and angle bracket 23. At the other end of the torque rod an arm 24 is fixed, to which the upper end of the pitch action compensator assembly 25 is attached. The lower end of the pitch action compensator is secured to the iron cross of the revolving Octagon (not shown) of the trainer.

'Also pivotally connected to the walking beam Il is a link 26 whose other end is pivotally connected as at 21a to a vertically mounted lever 21, swingable'on pivot 28 supported on pedestal 29. A straight rod 3I is connected at one end, as at 32, to a vertically mounted lever 33' whose pivot 34 is supported on pedestal 35. IAlink 30 joins lever 33 with walking beam I1 at an intermediate point, so that the walking beam swings lever 33 as well as lever 2l. It will be observed thatl these levers are swung in opposite directions. The other end of rod 3| is attached to a tension spring 36, whose opposite endis connected by an eye-bolt 38 and nut 33 to a bracket and more distant g the rear on arm 14 through an eye-bolt 16.

31 projecting from the movable Vleaf of the air speed regulating bellows 40. The iixed leaf of said bellows is supported by two brackets 4|, 42 on any xed support, and a needle valve (not shown, but carried on the iixed leaf) controls the vacuum suction through vacuum line 43, which connects the interior of the bellows and the lower vacuum manifold 44. The turbine (not shown) is connected with this manifold. Another pipe or tube45 connects the air speed regulating bellows 40 with the interior of bellows 46 of the stall valve to be described, and a branch tube 41 further connects the air speed regulating bellows with the air speed damping tank 48. At the upper end of lever 21 an eye-bolt 49 is se cured, and a tension spring B is connected to the other end of said eye-bolt and also to a bracket 5| fixed to and projecting from the movable leaf of tachometer-regulating bellows 52. Thetension of spring 50, also of spring 36, is adjustable by its eye-bolt. The iixed leaf of bellows 52 is secured to a pair of brackets 53, 54 by which bellows 52 is supported. A vacuum line 55, controlled by a needle valve (not shown) extends from the bellows 52 to lower vacuum manifold 44, and another vacuum line 56 extends from bellows 52 to tachonieter 51.

When the speed of an airplane drops below. a certain minimum, the airplane stalls and sometimes starts to spin. 'Ihis characteristic is built into the Link trainer. Stall valve 60 is supported on a plate 6| secured to the iioor of the fuselage of the trainer, and has a vent 62 open to the atmosphere, also a line 63 leading to the climbdive tank 64, to the climb-dive valve assembly (not shown) and to the altimeter and vertical speed indicator, likewise not shown. Anothertube 65 connects with the spin trip assembly (not shown) which starts the trainer spinning, in a manner well known to those' who are familiar with Link trainers. that the stall valve here illustrated is the old type, and that later models of trainers have a different stall valve construction and arrangement. Finally, a vacuum suction line 66 is connected to a source of vacuum (lower manifold 44) but with certain novel apparatus interposed in this line, as will be described. Now stall valve 60 is an oscillatory type of valve, that is, it ls turned on its longitudinal axis to open and close It should be understood- The other end of spring 15 is anchored to the upper end of a lever 11 pivoted at 18 upon a. pedestal 19. At its lower end, lever 11 is pivotally connected to a link rod 80 having a connection ywith the lower end of a vertical arm 8| fixed to torque rod 2|. Spring 15 obviously tends to open stall valve bellows 46, and will open it if the source of vacuum is shut off from the interior of said bellows. It is also clear that counter-clockwise oscillation of torque rod 2| (by means of throttle will cause lever 11 to swing counter-clockwise (as viewed in Fig. l) increasing the tension on spring 15 and perhaps opening bellows 46, the result depending on the difference in the opposing forces. At normal air speed" of the trainer, the vacuum suction is strong enough to keep bellows 46 collapsed, overcoming the tension of spring 15. Pivotally attached at one end to arm 14 is a straight rod 82 having adjustable stops 83 supported thereon and held in adjusted positions by set screws 84. A short rod 85 is received in stops 83 to form with rod 82 and said stops a four-sided enclosure for apin 85 extending horizontally through the slot in slotted pendulum bar .68 and ,adjustable along said bar by means of a nut, as will be understood without further illustration. Rod 82 rests on pin 86, hence is supported more or less horizontally, although attached at `one end only to arm 14. As pin 86 is contacted by stops 83 (which in turn are moved by arm 14 on the stall valve bellows), it will be pushed in one direction or the other, causing the pendulum to move to operate the stall valve. The described construction is a lost-motion connection between the stall valve bellows 46 and the pendulum which actuates the stall valve, but said pendulum is free to move, independently of stops 83, whenever the position of the trainer causes'it to swing.

The parts so far .described are well known to those 'acquainted with Link trainers, but are briefly mentioned so that the setting of the inv vention will be clearly understood.

various ports, unnecessary to illustrate, to control the suction through the lines 63, 65, 66'and through vent 52. Stall valve has a stem 61 fixed to the valve body and projecting from one en d, with an inverted pendulum fixed to the stem 61, said pendulum comprising a slotted bar 68 with a weight or bob 69 at its upper end. Plate 6| supports two diverging stationary arms 10, 1|- arranged in a V, with stop screws 12 threaded through the upper ends of said amis to serve as adjustable stops for the pendulum bar 68V. Since the stall valve is mounted on the iioor of the trainer, any substantial tilting of said floor will cause the pendulum to fall to one side or the other until it strikes one of the stopscrews 12. Simultaneously the stall valve will be oscillated to change the positions of its ports. Arm 10 has a bracket 13 fixed to its upper end, and stall valve bellows` 46 is secured to this bracket, being however free to expand and collapse.. The movable leaf 46a of bellows 46 has an arm 14 xed thereto, so as tomove when the bellows expands and collapses. and a tension spring 15 imposesa constant but adjustable pull the pendulum bob 94 being uppermost.

Interposed between vthe stall valve and the source of vacuum, also the air speed indicator 81, is the device of my invention, which may be termed an air speed control and spin-delay assembly. Its preferred position in the trainer fuselage 88 is indicated in Fig. 5, but other locations are feasible.

The preferred embodiment of my invention employs a. three-way valve 90 secured to a platform 9|. Valve 90 is generally similar to stall valve 60 and has an axial stem 92 to which the arm 93 of an inverted pendulum is attached, The pendulum swings between two adjustable stops 95, 96 in the form of screws threaded through brackets 91, 98, respectively, attached to platform 9|. The pendulum is biased to move to the left or counter-clockwise, as viewed in Fig. 1, by means of a tension spring 99 anchored by an eye-bolt |00 to an angle bracket |0| fixed to the fuselage. The other endof spring 99 is hooked vto a link |02 adjustably secured to one of a series of perforations |03 in an arm |04 nxed to the vbe increased or decreased by selection of diiferent perforations |03. Arm |04 is also connected by a wire |05 to the movable-leaf 46a of the stall valve bellows, and here again the moment arm is adjustable, as perforations |03 are also used for this connection.

ascenso The three-way valve 90 has three ports |06, |01, |08 (Fig. 3) in the valve body. Vacuum line B6 leads to one side of port |06, and another vacuum line |09 extends from the other side of said port to the upper manifold |'|0, which is open to the lower manifold'44. Thus when port |06 is open, as in the left bottom view of Fig. 3, the source of vacuum is connected to the stall valve. 'I'he middle port |01 is connected on one side by a tube to the air speed damping tank 48, and on the other side is connected by a tube ||2 to the tube ||3 which extends to the air speed indicator 81. The third port v|08 has an atmospheric vent ||4 on one side, and 'a tube ||2a coupled to the air speed indicator tube H3. The several positions of the ports |06, |01, |08I as the valve is moved with the inverted pendulum from position A, Fig. l to position B andI then to position C, are clearly shown in Fig. 3

, and require no further description.

sion on coil spring 38, thus opening the air speed regulating bellows 40. The needle valve (not shown, but described above) in bellows 40 is then moved so as to open -tube 45 to the suction through line 43 from the lower suction manifold 44. The partial vacuum or suction in tube- 45 exhausts air from the stall valve bellows 46,

- which collapses, moving bellows leaf-4|ia` and 9| and, if preferred, latch |8 may be vspringactuated. Latch lever ||5 is of spring metal,

and may have the necessary resiliency to move past the cam end of the latch ||8 and snap under theshoulder ||8a (Fig..2) when moved to the right or clockwise, as viewed in Fig. 1. If preferred, latch lever ||5 may be moved under shoulder-Illia by magnetism. To unlock (and if desired, to lock) the latch lever, a solenoid ||9 is flxed on the platform and has a plunger |20 which is projected,'when the solenoid is energized, to strike the latch lever and move it out from under catch llaa, whereupon the parts will act normally responsive to the pull of the spring and the opening or closing of the bellows 40a.n Solenoid ||9 is actuated by leads |2| which extend to a 110 v. ignition switch' circuit. Referring to Fig. 4, the 110 v. main leads |22 are causing arm 14 to move to the right, which moves the stall valve pendulum 68 to the right by ac- |05, which pulls arm |04 to the right, causing pendulum 93 to rise from the dotted line position, position A toward the full line position. However, as atmospheric vent ||4 is stillopen to the air speed line H3, the vacuum in said line is reduced. This retards the action of stall valve bellows 46, and pendulum 83 is slowly raised from position A to position B. Vacuum is then applied to linel ||3, and indicator 81 shows a slowly increasing air speed.l Finally the stall valve bellows through wire |05 will move the pendulum to position C, whereupon the described automatic latching takes place, and latch lever |15 is held beneath the shoulder ||8a of the latch. The trainer then reaches flying speed, according to indicator 81'. If at any time ying speed islost, port |06 will permitl the vacuum toact through the stall valve to collapse the spin trip .bellows (not shown), whereupon the trainer starts spincoupled to a. step-down transformer |23, to the low side of which a copper oxide rectifier |24 is shown connected. lA single-pole single-throw.

self-return switch |25 permits the student, or the instructor, to unlock valve 90 by momentarily closing the solenoid circuit. Latch lever ||5 is 'positionthe inverted pendulum 93,94 is in position A, and valve port |05 is closed, which cuts off the stall valve from the source of vacuum, and the spin trip assembly (not shown) which is operated through the stall valve, cannot trip to start the trainer spinning. This result (preventing the trainer from spinning) is accomplished even though the stall valve isrin proper position to start the spinning, and independently of any action by the instructor or student. When port |08 is closed (Fig. 3) port |01 is also closed, which prevents any indication of air speed at indicator 81. Port |08 is then open, which opens the air speed line ||3 to the atmosphere through vent ||4. When the throttle 'is advanced as for take-off, this swings walking beam |1 clockwise about its pivot 20, which swings lever 33 counterclockwise, pulling rod 3| to the right as viewed in Fig. V1 and increasing the tenning, as is desired when the simulated aircraft loses air speed. Spinning of the trainer is effected through a rudder valve (not shown) and continues until power is cut offu from the trainer or until the student manipulates the trainercontrols in such a vway as to regain normal flying speed (as shown on the indicator 81) Satisfactory operation of the air speed conto return valve 90 to position. By adjusting the tension of spring 90, the take-off speed of the trainer may be controlled, since the application of vacuum to the'air speed indicator 81 through line ||3 depends on the position of the threeway valve 80.

Obviously the invention has all the advantages set forth above. understood 'that the invention is not confined to the embodiment herein shown for the purpose of illustration, but may have various forms within the scope of the appended claims.

What I claim is:

1. In an instrument flying trainer of 'the tyie which employs a source of Vacuum and' a stall valve assembly for control of spinning of the trainer; said stall valve assembly having a bellows, a vacuum line leading to the bellows, a vacuum line leading to the stall valvel body, and'4 However, it should be latch lever fixed to the body of the last namedV valve, a latch' engageable withsaid latch lever, a solenoid,a switch, a source of electricity, and a circuit connecting the switch, solenoid and source of electricity; the solenoid operating to re.- lease the latch lever from thelatch when the switch is closed.

3. The invention according to claim 1, wherein the last named valve has a valve stem projecting therefrom; an -inverted pendulum fixed to the valve stem; stops to regulate the amount of swing permitted the pendulum; an arm fixed to said valve stem; said spring being connected to the mit said valve means to move into such position that the stall valve -will resume its normal operarm, and the means which connects the stall valve bellows with the last named valve also being connected with said arm, but in opposition to said` spring.

4. The invention according to claim i, wherein the trainer has an air speed indicator, an air.

speed damping tank, lines connecting the air speed damping tank with the source of vacuum4 -and the stall valve bellows; the last named valve 'being a three-way valve, with connections on one side to the atmosphere, to the air speed damping tank and to the suction side of the stall valve, and with Vconnections on the other sidel to the air speed indicator and to the source of vacuum.

5. In an instrument ying trainer of lthe type which' employs a source of vacuum and a stall valve assembly for control of spinning of the trainer, valve means interposed between the stall valve assembly and the source of vacuum, vacuum lines connecting said valve means with the stall valve. assembly and the source of vacuum, said valve means being constructed and arranged so that, when operation-of the trainer is started, the source of vacuum is cut oil from the stall valve assembly to o bviate automatic spinning of the trainer; and operator-controlled means to perating state.

6. In an instrument trainer having a source of vacuum, a stall valve,'a vacuum line for connecting the stall Valve to a spin trip assembly, said stall valve having a bellows which is collapsed by vacuum, and a tension spring connected to the bellows to tend to expand the same, the spring tension being overcome by the vacuum of normal operations; an 4air speed regulating bellows; a tension spring connected to. the air speed regulating bellows Aso that its' tension is overcome by the vacuum of normal operation; a vacuum line connecting thestaIlValVe bellows with the air speed regulating bellows; a vacuum line connecting the air speed regulating bellows with the Jsource of vacuum; an ai; speed damping tank; a

vacuum line connecting the air speed damping tank with the air speed regulating bellows; a valve for controlling operation-cf said stall valve; a vacuum line directly connecting the last named valve with the stall valve; means mechanically connecting the last named valve with the stall valve bellows; a vacuum line connecting the air speed damping tank with the last named valve; an atmospheric vent connected to the last named valve; a tension spring connected to the last named valve to tend to move the same in one direction, the tension of said spring being also transmitted through the mechanical connecting means to the stall valve bellows; an inverted pendulum attached to the last named valve and co-operating with the last named spring when `moving in one direction, and co-operating with the stall valve bellows when that bellows is nearly collapsed; an air-speed indicator; a tube con- -necting the air speed indicator with the last named valve; a vacuum line connecting the last named valve with the source of vacuum; means to latch the last named valve in the position in which thelast named valve transmits vacuum suction to the stall valve; and operator-controlled means to release the latching means.

. SHERMAN A. H'OLBERT. 

